Many clutched placards on which they had written their names and home towns in Arabic and English as they chanted: "Down, down Assad!" and "One solution: revolution!"

The "I am not afraid" protest, which was co-ordinated by Amnesty International, attracted around 40 Syrians from around the UK.

In contrast to previous demonstrations, when protesters have reported being photographed by embassy employees, there was no sign of diplomatic staff or attempted interference with the hour-long event.

Khalil Daaboul, a 25-year-old security guard originally from Lattakia in western Syria, said he had decided to protest to make it clear that he no longer feared the Assad regime.

"I was worried all the time before the uprising on 22 March, but when I saw the uprising I was not afraid any more," he said. "I rang my brother and said, 'I'm sorry if they arrest you, but I can't remain silent'."

Daaboul said he had left Syria because he had no wish to do his military service.

"Imagine if I was there now," he said. "They might make me kill my friends or my brother. I know what the military does … [but] I am sure the [Assad] regime will be changed as Syrians are saying enough is enough."

His sentiments were echoed by Razan Saffour, 18, a student from north west London.

"I'm down here to support our family in Syria and the show them that we're not scared," she said. "I don't think that anyone will allow this regime to stay. It may take a long time, but eventually [Assad] will go."

Ahmad Alhusari, a 22-year-old engineer from Glasgow, had left Scotland at 3am to make sure that he and his friends arrived in good time for the demo.

He said they had felt dutybound to protest even though he knew he had been photographed by embassy staff on previous occasions and his family had suffered during the uprising.

"[We would do] anything for Syria," he said. "If people there are willing to give their lives and face bullets and tanks, why should they frighten us here?"